Control means for opposed rams of a press

ABSTRACT

In an hydraulic press having opposed work performing rams a control for synchronizing the movements of the rams during their working strokes comprises several sets of limit switches for each ram arranged in the direction of the travel of the rams, the switches of similar sets being coordinated to interrupt the movement of the rams in the event an undesirable degree of travel occurs in one ram as compared with the other.

United States Patent 11 1 1111 3,

Kent et al. Nov. 19, 19 74 54] CONTROL MEANS FOR OPPOSED RAMS 2,729,9431/1956 03116 et al. 91 /171 3,050,809 8/1962 Kupka 100/264 X OF A PRESS3,435,719 4/1969 Wythe 83/623 [75] Inventors: Francis J sep ent, 1 g o3,648,565 3/1972 PlObSI et al 91/171 Seymour E. Steinbrook, wynnewoodboth of Primary Examiner-Billy J. Wilhite [73] Assignee: Wean United,Inc., Pittsburgh, Pa. Attorney, Agent, or Firm-Henry C. Westin; Daniel22 Filed: Aug. 30, 1973 Patch [21] Appl. No.: 393,237

[57] ABSTRACT [52] US. C 100/264, 20 In an hydraulic press havingopposed work performing 91/171 rams a control for synchronizing themovements of the [51] Int. Cl. B30b 15/18 rams during their workingstrokes comprises several Field of Search 1 4, sets of limit switchesfor each ram arranged in the di- 269 rection of the travel of the rams,the switches of simi- 91/171 lar sets being coordinated to interrupt themovement I of the rams in the event an undesirable degree of [56]References Cited travel occurs in one ram as compared with the other.

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CONTROL MEANS FOR OPPOSED RAMS OF A PRESS It is highly desirable incertain pressing operations where there are employed opposed travellingwork performing rams to maintain the travel of the rams within apredetermined degree of synchronization. This is particularly highlydesirable in press operations like compacting a deep stack of loosematerial which should be compressed simultaneously'from both ends. Thepurpose is obtaining uniformed density in the compact by equalizing theeffect of the friction on the walls of the container which encloses thematerial.

The present invention provides a control for assuring in a simple,economical and trouble-free manner the synchronization of opposingtravelling work performing rams of a press and for adjusting the degreeof synchronization.

More particularly, the present invention provides a control meansincluding a set of at least two movement detecting means for each ramarranged to be operated by their respective associated rams, and meanscoordinating the sets of movement detecting means in a manner tointerrupt movement of the rams in the event an undesirable degree oftravel occurs in one ram as compared with the other ram until thelagging ram reaches a desired synchronized position to the interruptedram.

Still more particularly, the present invention provides a control meansfor the purpose noted above comprising several sets of coordinated limitswitches for each ram arranged in spaced relationship in the directionof the working stroke of the rams, means for coordinating similar sets,as determined by their particular positions to their associated rams, sothat the rams will continue to move towards each until the limitswitches of the related sets are operated by their associated rams.

Another object of thepresent invention is to provide a control of thetype described immediately above in which the limit switches areconstructed and arranged so that initially on operation of the ramscertain limit switches are closed and are opened on engagement by theirassociated rams and other limit switches are opened and are closed byengagement by their associated rams, the limit switches that are openedserving to interrupt travel of their associated ram until the otherlimit switches have been closed.

Another object of the present invention is to adjust the degree ofsynchronization so that either ram does not advance far ahead of theother, but that, on the other hand, its movement is not interruptedunnecessarily if the difference in the travel of both rams is withinacceptable limits.

These objects, as well as other novel features and advantages of thepresent invention will become more apparent when the followingdescription of one embodi ment thereof is read along with theaccompanying drawings of which:

FIG. 1 is an elevational view of a double-ramhydraulic pressincorporating the features of the present invention; I

FIG. 2 is an enlargement of the ram displacement synchronization controlshown in FIG. 1, and

FIG. 3 is a schematic electrical control circuit for the control shownin FIG. 2.

In referring first to FIG. 1, there is shown in outline form anhydraulic press 10 having three vertically arranged tension columns l2,l4, and 16, and tied together at the top and bottom by entablatures l8and 20, respectively. The top entablature carries a number of pistoncylinder assemblies 22, 24, and 26, the ram ends of which are connectedto a crosshead 28 with whichthere is associated a top ram 30. Likewise,the bottom entablature 20 carries a number of piston cylinder assemblies32, 34, and 36, having their rams connected to a crosshead 38 with whichthere is associated-a working ram 40.

It will be appreciated that the illustrated press 10 may follow severalwell-known forms and for which reason further description of thestructure and operation of the press will not be given. It will behelpful, however, to note that associated with the press 10 is aturntable 42 for receiving a number of containers, two being shown at 44and 46, which serve to transfer the material to be compacted between therams 30 and 40 and after the compacting is completed to move the formedworkpiece away from the press while at the same time bringing a newcontainer between the rams.

As noted before, it is important that the rams 30 and 40 during theirworking stroke move in a synchronized relationship. As has been noted,the present invention provides a control that in a simple andtrouble-free manner accomplishes this purpose. Part of the control isshown in general form in FIG. 1 by the two control boxes 48 and 50arranged adjacent to the upper and lower movable crossheads 28 and 38,respectively. The control boxes 48 and 50 are best shown in FIG. 2 whichillustrates that each control box is made up of a number of limitswitches, the upper employing the letter A and the lower box employingthe letter B," such as LS-lA through 6A and LS-IB through 68,respectively. The lower numbers identify the limit switches closest totheir respective crossheads 28 and 38.

The limit switches can, be of several well-known types, the one beingemployed in the illustrated embodiment, although not shown, being of aroller-arm cam type. The schematic horizontal lines in FIG. 2 associatedwith each limit switch represent their lever arms and the vertical linesextending between two adjacent switches to form cooperative pairsrepresent the comparative distances between each pair. These distancesdetermine the degree of synchronization and are adjustable. As shown,the distance between the pairs of switches become progressively smalleras the crossheads move towards the final pressing stage sincesynchronization is less important at the beginning of the stroke of therams 30 and 40 than at the ends.

The electrical circuit for the limit switches LS-lA to 6A and LS-lB to6B is shown in FIG. 3. It includes two power lines 52 and 54 connectedtogether by a line 56 having a switch 58 shown in its opened position.FIG. 3 shows the coordinated relationship of the limit switches in whichit will be noted that limit switches LS- lA-3A and 5A are employed inparallel with limit switches LS-2B, 4B and 6B, respectively, andsimilarly limit switches LS-lB-3B and 5B are arranged in parallel withlimit switches LS-2A-4A6A, respectively. Each of the two interrelatedgroups of limit switches are associated with the different one of therams 30 and 40, each ram being controlled by a relay, theupper ram byrelay 1CR and the lower ram by relay 2CR arranged in a line 60.

As shown, LS-2B-4B-6B and LS-2A-4A-6A are initially closed whereas limitswitches LS-lA-3A-5A, 1B, 3B, and B are initially opened.

In this way, in referring for example to the cooperative sets of limitswitches 2-A and 1B and 1A and 28 current is allowed to pass over lines56 and 60 to operate the relays lCR and 2CR to effect initiation of theoperation of both rams 30 and 40. In examining the operation of thecircuit of FIG. 3 from first the standpoint of maintaining the ramsoperative when they are advancing at a proper rate of speed, as thecrosshead first trips their respective limit switches LS-IA and 18,these limit switches are closed and remain closed. Current thereforepasses to the relays lCR and 2CR through the contacts of limit switchesLS-lA and LS-lB even after the crossheads have tripped switches LS-2Band LS-2A, and opened their contacts. If the rams are still proceedingsynchronously limit switch 3A and LS-3B will be closed and remain closedand the rams will continue to function even though limit switches 8-4Aand 4B are contacted and opened and remain opened.

The same procedure takes place between the sets of limit switches 5B-6Aand 6B-SA. If however, one of the rams move slower or faster than theother ram, say for example, the ram 40 lags behind the ram 30, andassuming that this takes place at the very start of the operation of therams, the faster ram 30 will close limit switch LS-lA and the currentwill pass over the line 60 to the relay 2CR of the ram 40 through bothlimit switches LS-2B and LS-1A. As the ram 30 contacts limit switchLS-2A, this limit switch will be opened and since the ram 40 has not yetclosed limit switch 18, the operation of the ram 30 will be interrupteduntil the lagging ram 40 advances to trip the limit switch IE to closethis switch, which will then remain closed as LS-2A will remain opened.Thus, the control illustrated in FIG. 3 is designed to control thesynchronization of the rams 30 and 40 in designated zones irrespectiveof which ram is the lagging ram and irrespective of where the differencein speed takes place.

In accordance with the provisions of the patent statutes, we haveexplained the principles and operation of our invention and haveillustrated and described what we consider to represent the bestembodiment thereof.

We claim:

1. In a press having opposed rams and means for causing said rams toadvance towards each other during their working strokes,

a control means including a set of at least two movement detecting meansfor each ram arranged to monitor the movements of their associated rams,

said detecting means forming zones of variable lengths, and

means for coordinating said sets of movement detecting means in a mannerto interrupt movement of one of the rams in the event an undesirabledegree of travel occurs in one ram as compared with the other until thelagging ram reaches a desired synchronized position to the interruptedram.

2. In a press in accordance with claim 1, wherein said sets of movementdetecting means include several sets of coordinated limit switches foreach ram arranged in spaced-relationship to the direction of travel ofsaid rams in a manner to form zones of variable lengths,

means for coordinating similar sets of limit switches with respect tothe path of travel of their associated rams in a manner to synchronizethe travel of the rams by causing interruption of the operation of anadvancing ram and a continuation of the operation of a lagging ram untilall the limit switches of related sets have been operated on by theirassociated rams.

3. In a press according to claim 2, wherein said limit switches areconstructed and arranged so that initially on operation of the rams alimit switch of each set is closed and is opened and remains opened onmovement of their associated rams and a second limit switch of each setis opened and is closed and remains closed by movement of theirassociated rams, the limit switch of each set that is opened serving tointerrupt a travel of their associated rams until the limit switch ofthe same set has been closed.

1. In a press having opposed rams and means for causing said rams toadvance towards each other during their working strokes, a control meansincluding a set of at least two movement detecting means for each ramarranged to monitor the movements of their associated rams, saiddetecting means forming zones of variable lengths, and means forcoordinating said sets of movement detecting means in a manner tointerrupt movement of one of the rams in the event an undesirable degreeof travel occurs in one ram as compared with the other until the laggingram reaches a desired synchronized position to the interrupted ram. 2.In a press in accordance with claim 1, wherein said sets of movementdetecting means include several sets of coordinated limit switches foreach ram arranged in spaced-relationship to the direction of travel ofsaid rams in a manner to form zones of variable lengths, means forcoordinating similar sets of limit switches with respect to the path oftravel of their associated rams in a manner to synchronize the travel ofthe rams by causing interruption of the operation of an advancing ramand a continuation of the operation of a lagging ram until all the limitswitches of related sets have been operated on by their associated rams.3. In a press according to claim 2, wherein said limit switches areconstructed and arranged so that initially on operation of the rams alimit switch of each set is closed and is opened and remains opened onmovement of their associated rams and a second limit switch of each setis opened and is closed and remains closed by movement of theirassociated rams, the limit switch of each set that is opened serving tointerrupt a travel of their associated rams until the limit switch ofthe same set has been closed.